For inspecting the presence of disconnection in a circuit wiring (conductive pattern) on a circuit board, a method is employed which comprises the steps of supplying an inspection signal to the circuit wiring, detecting the inspection signal at the end or the like of the circuit wiring, and analyzing the detected signal. In terms of techniques for detecting the inspection signal at the end or the like of the circuit wiring, there have been proposed a contact type using a probe in contact with the circuit wiring, and a non-contact type using a sensor in non-contact with the circuit wiring.
In the non-contact type inspection, a temporally varying inspection signal is supplied to the circuit wiring, and a resulting signal arising at the non-contact sensor through a capacitance interposed between the non-contact sensor and the circuit wiring is detected to inspect the presence of disconnection or the like in the circuit wiring. As for the non-contact sensor, various types of sensors, such as an electrode type composed of a conductive metal plate or the like, or a semiconductor device
The non-contact type inspection is advantageous in that the circuit wiring is seldom damaged because the sensor is in non-contact with the circuit wiring, and such an inspection has wide applicability to fine-pitch circuit wirings.
One example of the non-contact type inspection is described, for example, in Japanese Patent Laid-Open Publication No. Hei 10-239371. This publication indicates one problem that the non-contact sensor cannot determine the presence of disconnection when used to inspect a circuit wiring having branch portions branched halfway therefrom, and describes an invention intended to solve the above problem by disposing a plurality of non-contact sensors over the ends of the branch portions of the circuit wiring, respectively.
However, the invention of Japanese Patent Laid-Open Publication No. Hei 10-239371 requires non-contact sensors disposed, respectively, over the ends of the branch portions or in the same number as that of the branch portions of the circuit wiring, and thereby the number of non-contact sensors inevitably tends to be increased. This is apt to drive up the cost of the inspection apparatus.
It is therefor a primary object of the present invention to provide an inspection apparatus and inspection method capable of inspecting a circuit wiring having branch portions branched halfway therefrom or a plurality of circuit wirings mixed with such a branched circuit wiring by using a less number of non-contact sensors.